1. ENTFACT-130
Bt-CORN: WHAT IT IS AND HOW IT WORKS
Ric Bessin, Extension Entomologist
Bt-corn is a type of genetically modified organism, European corn borer occurs. The protein is very
termed GMO. A GMO is a plant or animal that has been selective, generally not harming insects in other orders
genetically modified through the addition of a small (such as beetles, flies, bees and wasps). For this reason,
amount of genetic material from other organisms GMOs that have the Bt gene are compatible with
through molecular techniques. Currently, the GMOs on biological control programs because they harm insect
the market today have been given genetic traits to predators and parasitoids much less than
provide protection from pests, tolerance to pesticides, or broad-spectrum insecticides. The Bt endotoxin is
improve its quality. Examples of GMO field crops considered safe for humans, other mammals, fish, birds,
include Bt-potatoes, Bt-corn, Bt-sweet corn, Roundup and the environment because of its selectivity. Bt has
Ready soybeans, Roundup Ready Corn, and Liberty been available as a commercial microbial insecticide
Link corn. since the 1960s and is sold under many trade names.
These products have an excellent safety record and can
Genetically modified foods are foods derived from GMO be used on many crops until the day of harvest.
crops. For example, corn produced through
biotechnology is being used in many familiar foods, To kill a susceptible insect, a part of the plant that
including corn meal and tortilla chips. In addition, corn contains the Bt protein (not all parts of the plant
is used to make high fructose corn syrup, which is used necessarily contain the protein in equal concentrations)
as a sweetener in many foods such as soft drinks and must be ingested. Within minutes, the protein binds to
baked goods. While the FDA (U.S. Food and Drug the gut wall and the insect stops feeding. Within hours,
Administration) regulates genetically modified foods, it the gut wall breaks down and normal gut bacteria
considers Bt-corn to be nutritionally equivalent to invade the body cavity. The insect dies of septicaemia as
traditional corn. bacteria multiply in the blood. Even among Lepidoptera
larvae, species differ in sensitivity to the Bt protein.
To transform a plant into a GMO plant, the gene that
produces a genetic trait of interest is identified and Genetic Modification
separated from the rest of the genetic material from a Do Bt-corn hybrids differ only in that they possess the
donor organism. Most organisms have thousands of genetic code to produce the Bt protein? Not exactly. To
genes, a single gene represents only a tiny fraction of the add a trait to a crop plant, the gene must be inserted
total genetic makeup of an organism. along with some additional genetic material. This
additional genetic material includes a promoter
A donor organism may be a bacterium, fungus or even sequence that, in part, determines how the new trait is
another plant. In the case of Bt corn, the donor organism expressed in the plant. For example, the promoter may
is a naturally occurring soil bacterium, Bacillus cause to protein to be expressed in certain parts of the
thuringiensis, and the gene of interest produces a plants or only during a particular period of time. There
protein that kills Lepidoptera larvae, in particular, is a marker gene that allows plant breeders to easily
European corn borer. This protein is called the Bt delta determine which plants have been transformed.
endotoxin. Growers use Bt corn as an alternative to Herbicide and antibiotic tolerance promoters are
spraying insecticides for control of European and commonly used to identify transformed plants. There
southwestern corn borer. may also be a plasmid or vector sequence that allows for
rapid multiplication of the gene of interest in a bacterial
Bt Delta Endotoxin host prior to insertion in the crop plant.
The Bt delta endotoxin was selected because it is highly
effective at controlling Lepidoptera larvae, caterpillars. FDA Approval
It is during the larval stage when most of the damage by Federal food law requires premarket approval for food

2. additives, whether or not they are the products of
biotechnology. FDA treats substances added to food
products through recombinant DNA techniques as food
additives if they are significantly different in structure,
function or amount than substances currently found in
food.
However, if a new food product developed through
biotechnology does not contain substances that are
significantly different from those already in the diet, it
does not require premarket approval. Products that are
genetically engineered to provide pesticide traits, such
as resistance to the corn borer, are also subject to
regulation by the Environmental Protection Agency.
Currently, genetically modified foods in the United
States do not require special labeling to notify
consumers.
Revised: 11/03